The present invention relates to improvements in plastic film bags with pressure closable releasable rib and groove profile fasteners at the top.
In the development of thin plastic film bags, an objective to be served is to provide a bag which has pressure closable and reopenable continuous rib and groove profile fastener elements at the top. Such fastener elements must securely close the bag and resist accidental opening due to forces on the side walls of the bag which occur during stacking, handling and merchandising. In order to reduce the cost of the bag, the fastener profiles are made as lightweight as possible without jeopardizing the facility of the fasteners to hold the bag closed. The ability of the fastener to remain closed can be augmented by design of a fastener but also by design of the bag structure in relation to the fastener structure. Coaction between the bag wall panels and the fastener strips can be attained by structural design so that stresses and pulls on the bag wall, such as occur inadvertently, do not pull apart the fastener strips to open the rib and groove profile fastener elements.
An object of the invention is to provide an improved bag structure which has a greater resistance to opening wherein the bag is constructed with separate fastener strips attached to the inner wall surface of the panels.
A further object of the present invention is to provide an improved bag stretcher and method of making the same wherein the bag has a reclosable fastener at the top and can withstand pulls and shocks from handling and from the contents without accidental opening of the bag fastener.
A further object of the invention is to provide an improved structure and method of making the structure wherein forces on the wall panel of a flexible bag act in a shear mode on the reclosable fastener rather than on a peel mode.